I would think the treatment in Knight's book is about as minimal as one can
really take for SR and be true to your principles. Even here he talks about
slow clocks (even if to say that's not really the right way to talk about
it, yet he uses the light clock in his development). This treatment is WAY
beyond what I can do in the liberal arts class. Again my point is, to
counter what JD has said about NOT talking about slow clocks, masses
increasing, and lengths contracting (probably didn't say this last), IS that
these are the perceived phenomenon for someone coming from the Newtonian
model. In my mind, it is still what the traveling twin has to conclude when
faced with the final situation--that his clock must have run slow. Yes, the
full explanation doesn't require a slow clock, but as a being who spends
most of his life in a nearly Newtonian world, the slow clock explanation may
make more sense and CAN be made without really violating any fundamental
principles--being careful about what frame is viewing what frame.
Therefore, I would still approach SR (first pass or only pass with gen-ed
classes) from that view point--as do almost all the text books-- perhaps for
good reasons, not just laziness or to defy the pontifical pronouncements of
what is 'right' and 'wrong' coming from a few. ;-)
----- Original Message -----
From: "LaMontagne, Bob" <RLAMONT@providence.edu>
To: "Richard Tarara" <rbtarara@sprynet.com>; "Forum for Physics Educators"
<phys-l@carnot.physics.buffalo.edu>
Sent: Friday, February 29, 2008 12:07 AM
Subject: Re: [Phys-l] special ed/relativity
The basic concepts of Special Relativity are invariance (tying together all
the energy and momentum concepts from earlier in the course) and the
mass-energy identity. That can be covered in 3 days without the need for DOT
products or the like. Length contrraction and time dilation as a consequence
of the constancy of the speed of light can be covered on one day, invariance
on a second, and mass-energy on a third. I think John's point is not the
math but a matter of not squandering the time available with useless
concepts. Use the little time available to best advantage by only covering
what is actually correct.